MILLING CUTTER HEAD WITH SERRATED CARTRIDGES

Abstract: A milling cutter head intended primarily for aluminum machining comprises grooves (4) in which are mounted cutting insert-carrying cartridges (2) and spacer plates (3). Those sides of the cartridge and the spacer plate that are in contact are serrated in the same direction. The other side of the spacer plate and the side surface of the groove being in contact with it are serrated in a direction which is perpendicular to the first mentioned serration. In this way it is possible to independently of each other and precisely adjust the cutting edge both axially and radially.

Description: MILLING CUTTER HEAD WITH SERRATED CARTRIDGES The present invention relates to a milling cutter head in which the cutting inserts are carried by cartridges placed in grooves around the periphery of the head, whereby also a spacer plate is placed in each groove. The cutting edges can be finely adjusted radially and axially by forming the cartridges and the spacer plates with serrations according to the characterizing part of claim 1. Cutting tools with cutting elements placed circumferentially around the envelope surface of a milling cutter head are described in, for instance, DE- B-l -102 526. According to this patent specification, the cutting elements are fixed by a serrated wedge and a screw. However, this construction does not allow any precision adjustment of the cutting edge because any change in the radial or axial position is stepwise and not contiguous, each step representing the breadth of one serration. Moreover, this construction does not bring any safety against centrifugal forces. Also in US-A-3 214 825 a fastening arrangement is disclosed for cutting elements in a milling cutter body, comprising a plurality of serrated surfaces with the serration ways directed axially, radially and diagonally. Although this construction makes possible an adjustment in both axial and radial direction, it does not permit a linear adjustment or an independent adjustment of one of the two directions; the two adjustment directions are interdependent. Thus, a certain adjustment in, e.g., radial direction also results in a certain diagonal, and thereby also axial, displacement. Moreover, this adjusting and fixing arrangement requires a number of different pieces resulting in an unnecessarily complicated construction. Inter alia, it comprises two weak break wedges which often rupture due to fatigue. Furthermore, nor is this construction sufficiently safe to centrifugal forces. Thus, a first object of the present invention is to provide a milling tool that makes possible a very precise adjustment of the cutting edges, both axially and radially. A further object of the present invention is to provide a milling tool that makes possible a precise and mutually fully independent axial and radial adjustment . Still a further object of the present invention is to eliminate any risk whatsoever that any of the parts in the fastening arrangement is suddenly flung out due to centrifugal force. Still another object of the present invention is to obtain a well balanced milling cutter body which is not influenced at high cutting speeds, these being common at for instance aluminum machining. Still another object of the present invention is to attain a precise adjusting of the cutting edges in the milling cutter head axially and radially, with as few separate parts as possible. A still further object of the present invention is to provide a simple and stable cutting insert fastening construction, with as few separate components as possible. These and further objects have been achieved in a surprising manner by constructing a milling tool that comprises the features defined in the characterizing part of claim 1. For illustrative but non-limiting purposes, the invention will now be further described in relation with the appended drawings which show a preferred embodiment . Figure 1 shows a milling cutter head according to the invention in a perspective view, with one cutting position exploded. Figure 2 shows an insert-carrying cartridge according to the invention in an exploded view. Figure 3 shows a cartridge groove with the pertaining cartridge and spacer plate from above. Figure 4 shows a spacer plate according to the invention in an exploded view. A milling cutter head generally designated by 1 rotates around its central rotation axis Z. Around its peripheric envelope surface are provided recessed grooves 4, whose extension direction is substantially parallel to the rotation axis of the milling cutter head. Each groove 4 is intended to take up an insert- carrying cartridge 2 and a spacer plate 3. Cartridge 2 comprises an insert pocket 14 for the fastening of a suitable cutting insert 5 by a locking screw 6. The nature of the cutting insert is not an essential feature of the present invention. However, a suitable application area for the present invention is the machining of aluminum with cutting inserts comprising a diamond element at one of the cutting corners. According to the illustrated embodiment, the cutting insert is a single-sided indexable insert of square basic form. In the milling cutter head, in front of each cutting insert in the direction of rotation, there is provided a chip recess or chip pocket 22. The surfaces of cartridge 2 and spacer plate 3 facing each other are formed with serrations 15 and 17, respectively. Preferrably, these surfaces are serrated in their entireties. According to the shown embodiment, these serrations are substantially radial. Further, they are of course formed with the aim of fitting well in each other, i.e., they are shaped with the same ridge width, the same top angles and substantially the same depth between the ridges. The distance between two adjacent ridges is not critical for the present invention, however it is suitably between 0,5 and 3 mm, preferrably between 1 and 2 mm. The surface 18 of spacer plate 3 being opposite to surface 17 is also provided with serrations, preferrably in its entirety. The serration direction of this surface is substantially perpendicular to the one on surface 17, i.e., it is substantially parallel to the rotation axis of the milling cutter head. The angle between the two serration directions should not deviate by more than 2°, preferrably by no more than 0°30', from right angle, since radial and axial fine adjustment then can no longer be made independently of each other. Concerning the form and the measures of these serrations, the same is applicable as mentioned above in relation with serrations 15 and 17. Alternatively, the serration directions can be swapped. Thus, according to that embodiment, the serrations 15 and 17 are substantially parallel to the rotation axis of the milling cutter body, while the serrations 16 and 18 are substantially perpendicular thereto. As is best seen in Fig. 3, the two sidewalls 16 and 20 of cartridge groove 4 converge towards each other radially outwards. In this way, a guarantee is obtained against the cartridge and the spacer plate being radially flung out of the groove by the centrifugal force. The angle between surfaces 16 and 20 can be between 2 and 6°, preferrably between 3,5 and 4,5° . A tap 8 is inserted into an orifice in the bottom surface of groove 4, the head of this tap being eccentric in relation to the smooth, cylindrical part of the tap. This eccentric head is placed into a recess or a through-groove 13 on the back of the cartridge. The eccenter head is suitably provided with a hexagonal hole or similar for turning and axially adjusting the cutting edge on cutting insert 5. This turning of tap 8 is accomplished by sticking a hexagon key or similar through the hole 10. The diameter of this hole is smaller than the diameter of said eccenter head, in order to radially secure tap 8. For radial adjustment of the cutting edge screw 9 is used, which is threaded into the threaded hole 11 in the cartridge. This screw is also provided with a hexagonal hole or similar, in order to make a turning of it possible by a suitable key. This key is inserted through the hole 12, which has a smaller diameter than the threaded part 11. This smaller diameter brings two advantages: firstly, screw 9 is radially secured, and secondly, it is easier to hit the hexagonal hole on screw 9. Alternatively, the cartridge can be provided with holes for two screws 9. Since groove 4 tapers radially outwards, the cartridge and the spacer plate have to be inserted into the groove axially. In order to at all make the mounting of cartridge and spacer plate possible, a certain free gap is necessary between the unity cartridge-spacer plate and the sidewalls 16 and 20 of the groove, in order to get past the head of eccenter tap 8 which protrudes into groove 4, with the radially inner side of the cartridge, whereafter the cartridge can be pushed radially inwards, when groove 13 has come in level with the eccenter head, upto abutment with the bottom surface of groove 4. If the angle between surfaces 16 and 20 is called α and the head of eccenter tap 8 has a thickness b, then a gap of b- since between cartridge surface 23 and groove surface 20 is necessary to get past the head of the eccenter tap. E.g., if b is 4 mm and a. is 4°, then theoretically said gap should be at least 0,28 mm. Thereafter, the cutting edge is precisely adjusted radially by screw 9 and axially by eccenter tap 8. The adjusting in these two directions can be done completely independently from each other, whereby the attained position is suitably made with a so called thousandth gauge. When the predetermined axial and radial positions have been attained, the cutting position is fixed by the threaded clamping screws 7A and 7B, which are threaded into the threaded through-holes 21A and 21B, respectively, in the head body. These clamping screws 7A and 7B are brought to exert a direct pressure upon the substantially smooth surface 23 of the cartridge, whereby the cartridge and the spacer plate, and consequently also the cutting edge, are fastened and fixed in the desired position. According to the illustrated embodiment, there are two clamping screws 7A and 7B. However, it is also feasible to have, for instance, one or three clamping screws 7. Since the clamping screws 7 are mounted in a position substantially perpendicular to the radial direction, they are also secured in their positions against centrifugal forces. Besides, they have the advantage of not negatively influencing the outbalance of the milling cutter body. By the above described construction a measure accuracy of 2 μm has been achieved for the positioning of the cutting edges, both radially and axially. The adjustment range in axial and radial direction respectively, can be from 0,5 to 1,5 mm. The achieved, precise adjusting in two dimensions has made possible to obtain very smooth surfaces on the machined work- piece, for instance at aluminum machining. Furthermore, the possibility of after-adjusting the cutting position as often as desired due to the cutting edge being worn has significantly improved cutting economy, since the same cutting insert can be reground several times. This is very advantageous when using expensive cutting inserts, in particular those with an inlay element of diamond or cubic bore nitride at one of the corners of the cutting insert.

Claims: C L A I M S 1. A milling cutter head in which cutting inserts are carried by cartridges (2) placed in grooves (4) around the periphery of the milling cutter head, whereby also a spacer plate (3) is placed in each groove, c h a r a c t e r i z e d in that one side (16) of each groove is serrated and in contact with a correspondingly serrated side (18) on the spacer plate (3) , that one side (15) of the cartridge is serrated and in contact with a correspondingly serrated further side (17) on the spacer plate, this side being opposite to the first mentioned serrated side (18) of the spacer plate (3) , whereby the serration directions on the two sides (17, 18) of the spacer plate are substantially perpendicular to each other. 2. Milling cutter head according to claim 1, c h a r a c t e r i z e d in that the two sides (16, 20) of each groove (4) facing each other converge radially outwards in order to secure the cartridge (2) and the spacer plate (3) against centrifugal forces. 3. Milling cutter body according to claim 1 or 2, c h a r a c t e r i z e d in that an eccenter tap (8) for axially adjusting the cartridge (2) is arranged radially inwards in relation to the cartridge (2) , whereby the head of the eccenter tap (8) is in a recess or a groove (13) on the radially inner side of the cartridge, and in that a hole (10) ending in said recess or groove (13) is provided in the cartridge (2) , ' this hole being intended for the insertion of a suitable key for turning the eccenter tap (8) . 4. Milling cutter head according to any of the preceding claims, c h a r a c t e r i z e d in that a screw (9) for radially adjusting of the cartridge (2) is arranged in a substantially radially extending through-hole (11, 12) in the cartridge (2) . 5. Milling cutter head according to any of the preceding claims, c h a r a c t e r i z e d in that one or several clamping screws (7A, 7B) are arranged for pressing against the side (23) of the cartridge being opposite to the serrated side of the cartridge, this side being substantially smooth, thereby fastening both the cartridge and the spacer plate in the groove. 6. Milling cutter head according to claim 5, c h a r a c t e r i z e d in that there is a gap between the smooth side (23) of the cartridge and the adjacent side surface (20) of the groove, whereby the width of this gap is larger or equal to b- since, where b is the thickness of the head of the eccenter tap (8) and ce is the angle between the two facing side surfaces (16, 20) of the groove. 7. Milling cutter head according to any of the preceding claims, c h a r a c t e r i z e d in that the angle between the two facing side surfaces (16, 20) of the groove (4) is between 2 and 6°, preferrably between 3,5 and 4,5°.

Inventors: ALMERSAND AAKE, WERNER HEINZ, ALMERSAND, AAKE, WERNER, HEINZ
Applicants: SANDVIK AB
Application year: 1994
Main classification: B23C5
IPC codes: B23C5